Polyolefin contact lens molds and uses thereof

ABSTRACT

Contact lens molds and methods of producing soft cast-molded contact lens products are provided. The methods include placing a soft hydrophilic contact lens-forming composition in a cavity formed between a first mold member and a second mold member, subjecting the composition in the cavity to conditions effective to form a contact lens product from the composition, and repeating the placing and subjecting steps a plurality of times, thereby producing a plurality of soft contact lens products. At least the first mold members, and advantageously all of the first and second mold members, are injection-molded with a nucleated thermoplastic polyolefin resin having a melt flow rate in a range of 10 g/10 min to about 40 g/10 min.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/845,721, filed on Sep. 18, 2006, the contents of which are expresslyincorporated herein by reference.

BACKGROUND

This invention relates to the production of molded soft contact lenses.More particularly, the invention relates to polypropylene contact lensmolds and methods of making soft contact lenses, such as hydrogelcontact lenses, using such molds.

Morrill U.S. Pat. No. 5,843,346 discloses a method of cast molding rigidgas permeable (RGP) contact lenses employing mold sections made of athermoplastic polyolefin resin, such as polypropylene resin, having amelt flow rate of at least about 21 g/10 min. This patent discloses thatmold sections made of such high melt flow rate resins produce rigidcontact lenses with a higher consistency of optical quality relative tomold sections injection-molded from other thermoplastic polyolefinresins, i.e., thermoplastic polyolefin resins having a melt flow rate of20 g/10 min or lower.

Portnoy et al. U.S. Patent Publication No. 2004/0044106 refers to theabove-noted Morrill patent and (RGP) contact lenses. This publicationdiscloses the use of molds including nucleated, metallocene-catalyzedpolypropylene with melt flow rates lower than 100 g/10 min, desirablylower than 21 g/10 min, and including a nucleating agent. Melt flowrates of the polypropylene polymers were measured according to ASTMD1238 at 230° C., with a 2.16 kg load. Portnoy et al. disclose that suchmolds are useful for precision applications, such as molds for (RGP)contact lenses. Portnoy et al. focuses on the details of making thenucleated, metallocene catalyzed polypropylene and does not disclosecontact lenses other than rigid gas permeable (RPG) contact lenses.Moreover, Portnoy et al. does not disclose any particular benefits oradvantages of contact lenses produced using nucleated,metallocene-catalyzed polypropylene molds.

Ansell U.S. Patent Publication No. 2006/0051454 discloses the use ofmolds made from Ziegler-Natta catalyst-based polyolefin resin having amelt flow rate of less than 21 g/10 min, as per ASTM D 1238, to producesoft contact lenses. The Ansell publication discloses that molds made ofthe Ziegler-Natta polyolefin resin molds with a melt flow rate less than21 g/10 min have equivalent or better quality indications relative tomolds created with metallocene catalyst-based polypropylene, and thatlenses produced using a polyolefin mold material with a melt flow indexof less than 21 g/10 min can include a diminished number of holes,chips, and tears in the manufactured lenses. The Ansell publication doesnot disclose or suggest the use of a nucleating agent.

There is a continuing need to provide contact lenses, for example, softor hydrogel contact lenses, with good surface and optical properties ina consistent and cost effective manner.

SUMMARY

New lens molds and methods useful in producing soft contact lenses havebeen discovered. The present molds and methods provide contact lenseshaving consistent high optical quality, for example, producing lenseswith fewer surface defects and/or with less severe surface defectsand/or reduced optical distortion caused by surface defects. Further,the present molds and methods use reduced amounts of energy, shortencontact lens production cycle time and achieve reduced machinery wearand tear. Such advantageous results are relative to producing identicalsoft contact lenses from molds made of thermoplastic polyolefin, inparticular polypropylene, resin having a melt flow rate of less than 10g/10 min, for example 1.9 g/10 min. Moreover, it has been found thatthese benefits of producing soft contact lenses in accordance with thepresent invention can be obtained without requiring molds made ofthermoplastic polyolefin resins having a melt flow rate of at leastabout 21 g/10 min, as in the above-noted Morrill patent for rigid gaspermeable contact lenses, and without requiring molds made out ofZiegler-Natta catalyst-based polyolefin resin, as in the above-notedAnsell publication.

In one broad aspect of the invention, methods of producing soft contactlens products, for example, soft hydrophilic or hydrogel contact lensproducts, are provided, and comprise placing a soft lens-formingcomposition in a cavity formed between a first mold member and a secondmold member, subjecting the soft lens-forming composition in the cavityto conditions effective to form a contact lens product from thelens-forming composition, and repeating the placing and subjecting stepsa plurality of times, for example, at least about 100 times or at leastabout 1000 times or at least about 10,000 times, thereby producing aplurality of soft contact lens products. At least the first moldmembers, and advantageously all of the first and second mold members,comprise a nucleated thermoplastic polyolefin resin having a melt flowrate in a range of 10 g/10 min to about 40 g/10 min. The present methodsproduce a plurality of soft contact lens products having fewer surfacedefects and/or less severe surface defects and/or reduced opticaldistortion caused by surface defects relative to an identical pluralityof soft contact lens products produced in identical molds in which thefirst mold members comprise a thermoplastic polyolefin resin having amelt flow rate of less than 10 g/10 min, for example, 1.9 g/10 min.

In another aspect, the present invention is directed to a method ofproducing soft hydrophilic cast-molded contact lenses having enhancedsurface quality. Such method comprises: providing first and second moldmembers structured to be assembled together to form a lens-shaped cavitytherebetween, each of the first and second mold members comprises anucleated, thermoplastic polyolefin resin having a melt flow rate in arange of about 10 g/10 min to about 40 g/10 min; placing a softhydrophilic contact lens-forming composition in the cavity; forming asoft hydrophilic contact lens product from the soft hydrophilic contactlens-forming composition in the cavity; removing the soft hydrophiliccontact lens product from the first and second mold members; andrepeating the above-noted providing, placing, forming and removing stepsa plurality of times. The present method produces a plurality of softhydrophilic contact lens products having enhanced surface qualityrelative to an identically produced plurality of soft contact lensproducts made using first and second mold members comprisingthermoplastic olefin resin having a melt flow rate of 1.9 g/10 min.

In a further aspect of the invention, a method of producing softhydrophilic contact lenses is provided which includes forming aplurality of soft hydrophilic contact lens products from a softhydrophilic contact lens-forming composition in cavities formed by firstand second mold members and removing the soft hydrophilic contact lensproducts from the first and second mold members. This method comprisesusing first and second molds comprising a nucleated thermoplasticpolyolefin resin having a melt flow rate in a range of about 10 g/10 minto about 40 g/10 min, and producing a soft hydrophilic contact lens withenhanced surface quality.

In another aspect, methods are provided as recited in the presentclaims.

In another aspect, contact lens mold members, contact lens moldassemblies, and batches of contact lens mold assemblies are provided.

As an example, contact lens mold assemblies and batches thereof areprovided, as recited in the present claims.

The soft contact lens surface quality benefits of the present inventionare effectively demonstrated by considering a plurality of soft contactlens products made identically. For example, consideration of at leastabout 100 or at least about 1,000 or at least about 10,000 or a fullcommercial run or batch of such soft contact lens products demonstratethe enhanced surface quality achieved in accordance with the presentinvention, for example, relative to a plurality of soft lens productsproduced using different thermoplastic olefin resin molds, as set forthelsewhere herein.

All patents, patent publications and other publications identifiedherein are hereby incorporated in their entireties herein by reference.

These and other aspects and advantages of the present invention areapparent in the following detailed description and drawings in whichlike parts bear like reference numbers.

Any and all features described herein and combinations of such featuresare included within the scope of the present invention provided that thefeatures of any such combination are not mutually inconsistent. Inaddition, any feature or combination of features may be specificallyexcluded from any embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a contact lens mold assembly usefulin accordance with the present invention.

FIG. 2 shows a series of soft contact lenses produced usingpolypropylene contact lens molds having a melt flow rate of 1.9 g/10min.

FIG. 3 shows a series of soft contact lenses produced in accordance withone embodiment of the present invention.

FIG. 4 shows a series of soft contact lenses produced in accordance withanother embodiment of the present invention.

FIG. 5A is an illustration of a plan view image of a contact lensobtained using a knife edge optical system, the contact lens beingobtained from a contact lens mold formed of nucleated thermoplasticpolyolefin resin having a melt flow rate in a range of about 10 g/10 minto about 40 g/10 min.

FIG. 5B is an illustration of a plan view image of a contact lensobtained using a knife edge optical system, the contact lens beingobtained from a contact lens mold formed of a polyolefin resin having amelt flow rate of 1.9 g/10 min.

FIG. 6A is an illustration of a section of a contact lens obtained froma contact lens mold formed of nucleated thermoplastic polyolefin resinhaving a melt flow rate in a range of about 10 g/10 min to about 40 g/10min.

FIG. 6B is an illustration of a section of a contact lens obtained froma contact lens mold formed of a polyolefin resin having a melt flow rateof 1.9 g/10 min.

FIG. 7A is an illustrative graph illustrating an example of a thicknessprofile of a contact lens obtained from a contact lens mold formed ofnucleated thermoplastic polyolefin resin having a melt flow rate in arange of about 10 g/10 min to about 40 g/10 min. The Y-axis representsthe relative thickness where 1 is indicative of the maximum thickness ofthe contact lens, and the X-axis represents the relative distance acrossthe contact lens section where 0 is indicative of one edge of thecontact lens section and 1 is indicative of the diametrically opposededge of the contact lens section. The optical center of the contact lensis located at the mid-point between 0 and 1.

FIG. 7B is an illustrative graph illustrating an example of a thicknessprofile of a contact lens obtained from a contact lens mold formed ofnucleated thermoplastic polyolefin resin having a melt flow rate 1.9g/10 min. The Y-axis represents the relative thickness where 1 isindicative of the maximum thickness of the contact lens, and the X-axisrepresents the relative distance across the contact lens section where 0is indicative of one edge of the contact lens section and 1 isindicative of the diametrically opposed edge of the contact lenssection. The optical center of the contact lens is located at themid-point between 0 and 1.

DETAILED DESCRIPTION

A representative contact lens mold assembly for use in the presentmethods is shown in FIG. 1.

Specifically, referring to FIG. 1, a contact lens mold assembly, showngenerally at 10, includes a first or female mold member 12 coupled to asecond or male mold member 14 to form a lens-shaped cavity 15 which hasa circular periphery. In addition, the first and second mold members 12and 14 can be structured to produce a contact lens having a roundedposterior lens edge surface. However, other embodiments of the moldmembers 12 and 14 may form non-rounded lens edge surfaces. As shown inFIG. 1, lens-shaped cavity 15 contains a polymerizable contact lensprecursor composition 17, which is discussed in detail elsewhere herein.The first and second mold members 12 and 14 are made of thermoplasticpolyolefin resin and are interference fitted together. In particular,first and second mold members 12 and 14 are press fitted together atfirst peripheral region 16 (of first mold member 12) and secondperipheral region 18 (of second mold member 14). Thus, first and secondperipheral regions 16 and 18 are structured to be in direct, securingcontact when the mold 10 is assembled as shown in FIG. 1. The first andsecond mold members 12 and 14 can be securely joined or coupled togethersimply by moving one or both of the mold members toward each other untilthe peripheral regions 16 and 18 come into direct, securing contact.When it is desired to separate the first and second mold members 12 and14, the mold members can be pulled apart or a tool can be used toovercome the direct, securing contact at the peripheral regions 16 and18, preferably without causing substantial damage to at least one of thefirst and second mold members and to the ophthalmic lens product formedin the lens-shaped cavity.

The contact lens precursor composition 17 within the lens-shaped cavityoften includes one or more monomers, macromers, polymers, or otherreactive agents, and combinations thereof, which are polymerized, suchas by exposure to UV light and/or heat, to form a contact lens product.Other processing steps may include, without limitation, disassemblingthe mold assembly or demolding the mold assembly, removing the contactlens product from the first mold member or second mold member ordelensing the contact lens product from a mold member, extractingextractable materials from the contact lens product, for example,extracting extractable materials from a silicone hydrogel contact lensproduct, hydrating the extracted contact lens product, inspecting thecontact lens, packaging the contact lens, and sterilizing the contactlens. In certain lenses, a separate extraction step may not benecessary. The resulting contact lens is a cast-molded contact lens.

In accordance with one aspect of the present invention, at least one ofthe first and second mold members comprises a nucleated thermoplasticpolyolefin resin having a melt flow rate in a range of 10 g/10 min toabout 40 g/10 min. As used herein, the term “g/10 min” refers to gramsper 10 minutes. As used herein, the term “melt flow rate” denotes theindustry known standard ASTM D 1238-86. This parameter is usuallyavailable from suppliers of commercial resins. Such mold member ormembers may be conventionally produced, for example, by injectionmolding processing. According to preferred embodiments, both moldmembers are injection molded from one or more of such resins.

The mold sections may be injection molded from the presently usefulthermoplastic polyolefin resins by methods which are otherwise known inthe art. The tools for the injection molding are typically made frombrass, stainless steel or nickel or some combination thereof. Apreferred material for use with this invention is nickel-plated brass.

Any suitable thermoplastic polyolefin resin or mixture of such resinsmay be employed in the presently useful mold assemblies provided thatsuch resin or resins yield mold assemblies which function in accordancewith the present invention, for example, to provide high quality contactlenses, as set forth herein. As noted elsewhere herein, the presentlyuseful thermoplastic polyolefin resin or resins used in the first and/orsecond mold members have a melt flow rate in a range of 10 g/10 min toabout 40 g/10 min. Examples of such thermoplastic polyolefin resinsinclude, without limitation, thermoplastic polyethylene resins,thermoplastic polypropylene resins, thermoplastic polystyrene resins,and the like and mixtures thereof. The presently useful thermoplasticpolyolefin resins can be made in any suitable manner, for example, usingconventional and well known processing. Therefore, a detaileddescription of such processing is not presented here. In one embodiment,the thermoplastic polyolefin resins useful in the present invention areother than Ziegler-Natta catalyst-based polyolefin resins. Particularlyuseful thermoplastic polyolefin resins are selected from thermoplasticpolypropylene resins and mixtures thereof.

The presently useful mold members which include such thermoplasticpolyolefin resins often contain a major amount, that is at least about50% by weight, for example, at least about 70% or at least about 90% ormore, by weight, of such resins.

The thermoplastic polyolefin resin or resins used in the mold assembliesin accordance with the present invention advantageously contain anucleating agent, an agent specifically or primarily utilized toincrease the rate of crystallization of the polyolefin component as itcools from the melt as compared to the same or identical polyolefincomponent without the nucleating agent. Many nucleating agents aresuitable for inclusion with the thermoplastic polyolefin resinformulations useful in the present invention. Suitable nucleating agentsare disclosed by, for example, H. N. Beck in Heterogeneous NucleatingAgents for Polypropylene Crystallization, 11 J. APPLIED POLY. SCI.673-685 (1967) and in Heterogeneous Nucleation Studies on Polypropylene,21 J. POLY. SCI.: POLY. LETTERS 347-351 (1983). Examples of suitablenucleating agents include, without limitation, sodium benzoate, sodiumsulfate, sodium 2,2′-methylenebis(4,6-di-tert-butylphenyl) phosphate,aluminum 2,2′-methylenebis(4,6-di-tert-butylphenyl) phosphate,dibenzylidene sorbitol, di(p-tolylidene) sorbitol,di(p-ethylbenzylidene) sorbitol, bis(3,4-dimethylbenzylidene) sorbitol,and N′,N′-dicyclohexyl-2,6-naphthalenedicarboxamide, salts ofdisproportionated rosin esters, and the like and mixtures thereof. Avery useful nucleating agent is sodium sulfate.

Without wishing to limit the present invention to any particular theoryof operation, it is believed that the presence of an effective amount ofnucleating agent in the thermoplastic polyolefin resin acts to reducethe time required for crystallization of the polyolefin resin and/or toproduce smaller crystals of the polyolefin resin relative to anidentical thermoplastic polyolefin resin without the nucleating agent.Reducing polyolefin crystallization time is believed to allow for betterand more precise control of polyolefin resin crystallization. Producingsmaller polyolefin resin crystals is believed to allow the polyolefinresin (crystallized) to more closely conform to the desired shape of themold member or members, in particular to the desired shape of thesurface or surfaces of the mold member or members which are shaped toproduce the anterior and/or posterior surfaces of the contact lensproduct. For example, the presence of a nucleating agent may at leastassist in reducing shrinkage time of the mold member or members, forexample, during processing to produce contact lens products relative tosuch shrinkage time in identical mold member/members in the absence ofthe nucleating agent. Ultimately, such reduced crystallization timesand/or smaller crystals and/or reduced mold member shrinkage time arebelieved to at least facilitate producing mold members with surfaceswhich result in contact lens products and hydrated contact lenses withreduced or less severe surface defects and/or reduced or less severeoptical distortion caused by surface defects, which benefits of thepresent invention are described elsewhere herein.

The nucleating agent may be included with the thermoplastic polyolefinresin at the resin manufacturing facility or may be added to the resinafter resin manufacture and prior to producing the mold member ormembers. The amount of nucleating agent employed may vary based on, forexample, the specific nucleating agent employed, the specificthermoplastic polyolefin resin employed, the specific completeformulation of the mold members employed and the like factors. Thenucleating agent may be present in an amount in a range from about 0.01%to about 2% (wt/wt). For example, in certain embodiments, the moldmember or mold members comprise from about 0.1% to about 1.5% (wt/wt) ofa nucleating agent. More specifically, embodiments of the present moldmember or mold members may comprise about 0.2%, about 0.4%, about 0.5%,about 0.6%, about 0.8%, or about 1.0% (wt/wt) of a nucleating agent.

Other additives may be included in the thermoplastic polyolefinformulations used to produce the mold members. The thermoplasticpolyolefin formulation may include an antioxidant to deter oxidativedegradation of the polymer and/or an acid scavenger to neutralizecatalyst residues which may be present in the resin. Examples of usefulantioxidants include, without limitation, hindered phenolicantioxidants, hindered amine light stabilizers, and the like andmixtures thereof. Examples of useful acid scavengers include, withoutlimitation, metal salts of weak fatty acids such as sodium, calcium, orzinc stearate and weakly basic minerals such as hydrotalcite, and thelike and mixtures thereof.

In one embodiment, a stabilizer component may be added to thethermoplastic polyolefin resin to stabilize the resin to oxidativedegradation during high temperature processes or during storage atelevated temperatures. Examples of the organic phosphorous acid esters(phosphites) such as trinonylphenol phosphite and tris(2,4-di-t-butylphenyl) phosphite, distearyl, hydroxylamine,5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuranone, distearylthiodipropionate, other fatty esters of thiodipropionic acid, and thelike and mixtures thereof.

Many other types of additives can be included in the thermoplasticpolyolefin resin formulations useful in this invention. Such otheradditives include without limitation, lubricants, antistatic agents,slip agents, anti-blocking agents, colorants, metal deactivators, moldrelease agents, fillers and reinforcements, fluorescent whiteningagents, biostabilizers, and the like and mixtures thereof.

Representative commercial polypropylene materials having the definedmelt flow rate include the following wherein melt flow rate (MFR) isindicated in g/10 min: the polypropylene resins available under thetrade name or designation Total 3622 (Total Petrochemicals USA, Inc.,MFR 12; Achieve 1654E1 (Exxon Mobil Chemical Co.) MFR 16; P4C5N-046,P4C6N-041 (Huntsman Polymers Corp.) MFR 20 and 35, respectively; Pro-FaxPDC 1288 (Basell Polyolefins) MFR 12; 10-7234 (BP Amoco ChemicalCompany) MFR 12.6; Marlex HLN-200 (Phillips Sumika PolypropyleneCompany) MFR 20; and FT-120-WV, ZS-751 and ZP-761 (Sunoco Chemicals) MFR12.0, 22.0, and 12.0 respectively. Another thermoplastic polyolefinresin suitable for use in a polyolefin copolymer (one of the olefinsbeing propylene) available under the designation PLTD 1870 (Exxon MobilChemical Company) MFR 16.

A number of the above-noted polypropylene products are nucleated, thatis such products include a nucleation agent which is effective in atleast assisting in controlling polymer crystallinity.

In one embodiment, once the first and second mold members are produced,such as injection molded, or otherwise provided, the present methodscomprise placing a soft lens-forming composition in a cavity formedbetween the first and second mold members or placing a soft lens-formingcomposition on a portion of one mold member and placing the other moldmember in contact therewith to form a lens shaped cavity containing thecomposition; and subjecting the soft lens-forming composition in thecavity to conditions effective to form a soft contact lens product fromthe soft lens-forming composition. The placing and subjecting steps arerepeated a plurality of times for a plurality of contact lens molds,thereby producing a plurality of soft contact lens products. Suchplurality of soft contact lens products have surprisingly been found tohave fewer surface defects and/or less severe surface defects and/orreduced optical distortion caused by surface defects relative to anidentical plurality of soft contact lens products produced in identicalmolds in which the first mold members comprise a thermoplasticpolyolefin resin having a melt flow rate of less than 10 g/10 min., forexample, a thermoplastic polyolefin resin having a melt flow rate of 1.9g/10 min.

In other words, the present invention provides for fewer surface defectsand/or less severe surface defects and/or reduced optical distortioncaused by surface defects in multiple lenses made in accordance with thepresent invention. For example, the placing and subjecting steps mayadvantageously be repeated at least about 100 times or at least about1,000 times or at least about 10,000 times. For example, a polymerizablelens precursor composition can be dispensed or placed in the cavities ofa plurality of the contact lens molds disclosed herein, such as at leastabout 100 lens molds or at least about 1,000 lens molds or at leastabout 10,000 lens molds. The placement steps can be practiced inparallel or serially or both. For example, for a batch of 100 contactlenses, the methods can comprise four steps of placing the lensprecursor composition in the cavities of 25 molds, ten steps of placingthe lens precursor composition in the cavities of 10 molds, ortwenty-five steps of placing the lens precursor composition in thecavities of 4 molds.

In one embodiment, both the first and second mold members comprise anucleated thermoplastic polyolefin resin having a melt flow rate in arange of 10 g/10 min to about 40 g/10 min, and the first and second moldmembers of the identical molds comprise the thermoplastic polyolefinresin having a melt flow rate of less than 10 g/10 min, for example, 1.9g/10 min or less than 1.9 g/10 min.

The present invention is particularly advantageous when the plurality ofsoft contact lens products are hydrogel contact lens products orsilicone hydrogel contact lens products. Some examples of the contactlens products are hydroxyethylmethacrylate (HEMA)-based contact lenses.

In one embodiment, with the first and second mold members assembledtogether, a silicone hydrogel precursor composition or anon-silicon-containing hydrogel precursor composition is located in thelens-shaped cavity formed between the first and second mold members.

As used herein, the term “hydrogel” refers to a network or matrix ofpolymer chains, some or all of which may be water-soluble, and which maycontain high percentages of water. Hydrogels refer to polymericmaterials, including contact lenses, that are water swellable or waterswelled. Thus, a hydrogel may be unhydrated and be water swellable, or ahydrogel may be partially hydrated and swollen with water, or a hydrogelmay be fully hydrated and swollen with water. The term “siliconehydrogel” or “silicone hydrogel material” refers to a hydrogel thatincludes a silicon component or a silicone component. For example, asilicone hydrogel includes one or more silicon-containing polymers. Asilicone hydrogel contact lens is a contact lens, including a visioncorrecting contact lens, comprising a silicone hydrogel material.

A silicone-containing component is a component that contains at leastone [—Si—O—Si] group, in a monomer, macromer or pre-polymer. The Si andattached O may be present in the silicone-containing component in anamount greater than 20 weight percent, for example greater than 30weight percent of the total molecular weight of the silicone-containingcomponent. Useful silicone-containing components comprise polymerizablefunctional groups such as acrylate, methacrylate, acrylamide,methacrylamide, N-vinyl lactam, N-vinylamide, and styryl functionalgroups. Examples of some silicone-containing components which are usefulin the present lenses may be found in U.S. Pat. Nos. 3,808,178;4,120,570; 4,136,250; 4,153,641; 4,740,533; 5,034,461 and 5,070,215, andEuropean Patent No. EP080539. Examples of silicone hydrogel contact lensmaterials have US Adopted Names of lotrafilcon A, lotrafilcon B,senofilcon A, galyfilcon A, balafilcon A, and comfilcon A.

Further examples of suitable silicone-containing monomers arepolysiloxanylalkyl(meth)acrylic monomers including, without limitation,methacryloxypropyl tris(trimethylsiloxy) silane, pentamethyldisiloxanylmethyhmethacrylate, and methyldi(trimethylsiloxy)methacryloxymethylsilane.

One useful class of silicone-containing components is apoly(organosiloxane) prepolymer such as α, ω-bismethacryloxy-propylpolydimethylsiloxane. Another example is MPDMS (monomethacryloxypropylterminated mono-n-butyl terminated polydimethylsiloxane). Another usefulclass of silicone containing components includes silicone-containingvinyl carbonate or vinyl carbamate monomers including, withoutlimitation,1,3-bis[4-(vinyloxycarb-onyloxy)but-1-yl]tetramethylisiloxane3-(vinyloxycarbonylthio) propyl-[tris(trimethylsiloxysilane];3-[tris(trimethylsiloxy)silyl] propyl allyl carbamate;3-[tris(trimethylsiloxy)wilyl] propyl vinyl carbamate;trimethylsilylethyl vinyl carbonate; and trimethylsilylmethyl vinylcarbonate.

In addition to the silicon-containing component, the present lenses,lens products, and compositions may include one or more hydrophiliccomponents. Hydrophilic components include those which are capable ofproviding at least about 20%, for example, at least about 25% watercontent to the resulting lens when combined with the remaining reactivecomponents. Suitable hydrophilic components may be present in amountsbetween about 10 to about 60 weight % based upon the weight of allreactive components. About 15 to about 50 weight %, for example, betweenabout 20 to about 40 weight %. Hydrophilic monomers that may be used tomake the polymers for the present lenses have at least one polymerizabledouble bond and at least one hydrophilic functional group. Examples ofpolymerizable double bonds include acrylic, methacrylic, acrylamido,methacrylamido, fumaric, maleic, styryl, isopropenylphenyl,O-vinylcarbonate, O-vinylcarbamate, allylic, O-vinylacetyl andN-vinyllactam and N-vinylamido double bonds. Such hydrophilic monomersmay themselves be used as crosslinking agents. “Acrylic-type” or“acrylic-containing” monomers are those monomers containing the acrylicgroup (CR′H═CRCOX) wherein R is H or CH₃, R′ is H, alkyl or carbonyl,and X is O or N, which are also known to polymerize readily, such asN,N-dimethylacrylamide (DMA), 2-hydroxyethyl acrylate, glycerolmethacrylate, 2-hydroxyethyl methacrylamide, polyethyleneglycolmonomethacrylate, methacrylic acid, acrylic acid and mixtures thereof.

Hydrophilic vinyl-containing monomers which may be incorporated into thematerials of the present lenses may include monomers such as N-vinyllactams (e.g. N-vinyl pyrrolidone (NVP)), N-vinyl-N-methyl acetamide,N-vinyl-N-ethyl acetamide, N-vinyl-N-ethyl formamide, N-vinyl formamide,N-2-hydroxyethyl vinyl carbamate, N-carboxy-β-alanine N-vinyl ester. Inone embodiment, the hydrophilic vinyl-containing monomer is NVP.

Other hydrophilic monomers that can be employed in the present lensesinclude polyoxyethylene polyols having one or more of the terminalhydroxyl groups replaced with a functional group containing apolymerizable double bond. Examples include polyethylene glycol with oneor more of the terminal hydroxyl groups replaced with a functional groupcontaining a polymerizable double bond. Examples include polyethyleneglycol reacted with one or more molar equivalents of an end-cappinggroup such as isocyanatoethyl methacrylate (“IEM”), methacrylicanhydride, methacryloyl chloride, vinylbenzoyl chloride, or the like, toproduce a polyethylene polyol having one or more terminal polymerizableolefinic groups bonded to the polyethylene polyol through linkingmoieties such as carbamate or ester groups.

Additional examples are the hydrophilic vinyl carbonate or vinylcarbamate monomers disclosed in U.S. Pat. No. 5,070,215, and thehydrophilic oxazolone monomers disclosed in U.S. Pat. No. 4,190,277.Other suitable hydrophilic monomers will be apparent to one skilled inthe art. More preferred hydrophilic monomers which may be incorporatedinto the polymer of the present invention include hydrophilic monomerssuch as N,N-dimethyl acrylamide (DMA), 2-hydroxyethyl acrylate, glycerolmethacrylate, 2-hydroxyethyl methacrylamide, N-vinylpyrrolidone (NVP),and polyethyleneglycol monomethacrylate. In certain embodiments,hydrophilic monomers including DMA, NVP and mixtures thereof areemployed.

Additional examples of materials used to make silicone hydrogel contactlenses include those materials disclosed in U.S. Pat. No. 6,867,245.

The non-silicon-containing hydrogel precursor compositions comprisemonomers or monomer mixtures which are polymerized to formnon-silicon-containing soft or hydrogel contact lens products in themold assembly comprised of the two mold members or halves include,without limitation, 2-hydroxyethylmethacrylate (“HEMA”), and HEMA andone or more comonomers such as 2-hydroxyethyl acrylate, methyl acrylate,methyl methacrylate, vinyl pyrrolidone, N-vinyl acrylamide,hydroxypropyl methacrylate, isobutyl methacrylate, styrene, ethoxyethylmethacrylate, methoxy triethylene/glycol methacrylate, glycidylmethacrylate, diacetone acrylamide, vinyl acetate, acrylamide,hydroxytrimethylene acrylate, methoxyethyl methacrylate, acrylic acid,methacrylic acid, glycerol methacrylate, dimethylamino ethyl acrylateand the like.

The non-silicon-containing precursor compositions preferably contain asmall amount of a cross-linking agent, usually from 0.05 to 2% and mostfrequently from 0.05 to 1.0%, of a diester or triester. Examples ofrepresentative cross linking agents include: ethylene glycol diacrylate,ethylene glycol dimethacrylate, 1,2-butylene dimethacrylate,1,3-butylene dimethacrylate, 1,4-butylene dimethacrylate, propyleneglycol diacrylate, propylene glycol dimethacrylate, diethylglycoldimethacrylate, dipropylene glycol dimethacrylate, diethylene glycoldiacrylate, dipropylene glycol diacrylate, glycerine trimethacrylate,trimethylol propane triacrylate, trimethylol propane trimethacrylate,and the like. Typical cross-linking agents usually, but not necessarily,have at least two ethylenically unsaturated double bonds.

The non-silicon-containing precursor compositions generally also includea catalyst, usually from about 0.05 to 1% (w/w) of a free radicalcatalyst. Typical examples of such catalysts include lauroyl peroxide,benzoyl peroxide, isopropyl percarbonate, azobisisobutyronitrile andknown redox systems such as the ammonium persulfate-sodium metabisulfitecombination and the like. Irradiation by visible light, ultravioletlight, electron beam or a radioactive source may also be employed tocatalyze the polymerization reaction, optionally with the addition of apolymerization initiator. Representative initiators includecamphorquinone, ethyl-4-(N,N-dimethyl-amino)benzoate, and4-(2-hydroxyethoxy)phenyl-2-hydroxyl-2-propyl ketone.

Polymerization of the monomer or monomer mixture in the mold assembly ispreferably carried out by exposing the composition to polymerizationinitiating conditions. The preferred technique is to include in thecomposition, initiators which work upon exposure to thermal radiation;and exposing the composition to thermal radiation of an intensity andduration effective to initiate polymerization and to allow thepolymerization of the composition to proceed to form a polymerizedcontact lens product.

After polymerization of the lens precursor composition, the moldassembly can be demolded, the polymerized contact lens product can bedelensed from one of the mold members, either the female or male moldmember, the delensed contact lens product can then be inspected andpackaged in a packaging solution, and sterilized. In certainembodiments, such as silicone containing hydrogel contact lenses, thedelensed contact lens product can be extracted and hydrated prior topackaging the lenses in a packaging solution.

With the present molds and methods, substantial improvements in thepercentage of commercially acceptable contact lenses can be obtained.For example, with the present molds and methods, a greater percentage ofa batch of contact lenses satisfies requirements for the commercialproduction of contact lenses. Examples of such requirements include lensdiameters, base curves, thicknesses, surface smoothness, overall shape,and the like. Thus, the amount of lenses that must be discarded due tomanufacturing variability and/or defects can be greatly reduced. Thepresent molds and methods can result in hydrated soft hydrogel contactlenses that are produced with a commercial acceptability rate of atleast 70%, at least 80%, or at least 90%. In other words, with thepresent molds and methods, less than 30%, less than 20%, or less than10% of the pre-hydrated or hydrated contact lenses must be discarded dueto manufacturing variability or defects. For example, conventionalhydrogel contact lenses can be produced with a commercial acceptabilityrate of at least 90%, or at least 95%. For example, at least 90 of 100or at least 95 of 100 lenses are acceptable and free of surface defects.In addition, silicone hydrogel contact lenses obtained from the presentmolds can be produced with a commercial acceptability rate of at least80%, for example, at least 80 of 100 silicone hydrogel contact lensesare acceptable and free of surface defects. The commercial acceptabilityof the contact lenses and/or polymerized contact lens products can bedetermined using conventional techniques and methods. For example, thelenses can be inspected one or more times, either visually orautomatically using one or more computerized machines, to ensure thatthe manufactured lenses are within predetermined manufacturingtolerances and are free of defects. The commercial acceptability ratecan be determined by calculating the number of contact lenses from abatch or plurality of contact lenses that must be discarded beforedistribution to consumers.

As one example, the number of contact lenses obtained from the presentmolds with visually smooth surfaces is greater than the number ofcontact lenses obtained from molds injection molded with a thermoplasticpolyolefin resin having a melt flow rate of 1.9 g/10 min. The surfacequality of the present lenses is visually noticeable using a magnifierat a magnification of at least 28×. One example of a device that can beused to view the lenses for surface defects is described in U.S. Pat.No. 4,784,485. A significant number of lenses obtained from contact lensmolds injection-molded with a thermoplastic polyolefin resin having amelt flow rate of 1.9 g/10 min have a surface that is not acceptable oris defective. These defective surfaces have a visible texture thatappears similar to a wavy texture or an orange peel or mottled textureon a scale from about 0.2 μm to about 2 μm scale. In other words,instead of a smooth surface, the surface of such defective lenses ischaracterized by the presence of hills or peaks and valleys. Forexample, a contact lens with a wavy texture can have a surface that hasvisibly noticeable undulations in the appearance of waves. Theundulations may have a sinusoidal shape when viewed in cross-section,and the period of undulations or waves can be regular or irregular.Orange peel texture observed on these defective lenses can be describedas appearing like the surface of an orange peel or otherwise mottledcharacterized by regions of peaks and regions of valleys. That is, thesurface of the lens has a visibly irregular surface characterized byrandomly spaced hills or peaks and valleys. Examples of such defectivelenses are shown in FIG. 2.

The surface defects of contact lenses are directly transferred from theplastic molds, which are injection-molded using a thermoplasticpolyolefin having a melt flow rate of less than 10 g/10 min, such as 1.9g/10 min. Due to the low melt flow rate, there are tremendous pressureloss and temperature drop for the molten flow fronts during the fillingphase of the injection molding process. The unpleasant moldingconditions can cause the surface defects on the plastic molds, which areused to cast contact lenses. When the contact lenses are made withdefective molds, they will have the same or similar surface defects.Particularly, when the contact lenses swell to become larger duringextraction and hydration processes, those surface defects become largeras well. The wavy and orange peel surface textures can have adverseeffects on lens optical and vision quality. These adverse effects shouldbe minimized or eliminated during the commercial production of contactlenses.

While the presence of waves or orange peel surface texture is visiblyapparent when the contact lens is viewed at 28× magnification with alens viewing instrument, such as a knife edge optical system, and thelike, these surface defects can be further characterized when thecontact lens is viewed in cross-section, or when the contact lens isanalyzed using a measurement device such as an interferometer and thelike. One example of an interferometer useful in quantifying the surfacedefects of contact lenses obtained from the present molds is the μPhase®FST 10 (Fisba Optik, Rochester, N.Y.).

A cross-section of the lens can provide an indication of the contactlens thickness from the contact lens peripheral edge to the opticalcenter of the lens, and possibly to the opposing peripheral edge. In acontact lens having smooth surfaces, the thickness is controlled andcorresponds to the distance between the surface of the first moldsection and the surface of the second mold section that define thecontact lens shaped cavity of the contact lens mold assembly. Thesurface of such lenses can be described mathematically, such as by usingZernike terms and wave-front analysis to fit the wavefront error of alens for a given field point. However, in a contact lens with a surfacedefect, such as wave texture or orange peel texture, the thicknessvaries and the thickness profile (e.g., a map of the thickness from thelens edge towards the optic center of the lens or a diametricallyopposing edge) is irregular and is characterized by peaks and valleys.The distance between a peak and adjacent valley on the thickness profileof a lens with a surface defect, as described herein, can be on theorder of about 0.2% of the target thickness of the lens as determined bythe distance between the two opposing surfaces defining the lens-shapedcavity of the contact lens mold assembly at the same distance from thelens edge periphery or perimeter of the lens shaped cavity. Or, thedistance between a peak and adjacent valley on the thickness profile ofa lens with a surface defect, as described herein, can be on the orderof about 2.0% of the target thickness of the lens as determined by thedistance between the two opposing surfaces defining the lens-shapedcavity of the contact lens mold assembly at the same distance from thelens edge periphery or perimeter of the lens shaped cavity.

Alternatively, the surface defects can be quantified by using ameasurement device such as an interferometer. Interferometers arepublicly available from companies, such as Fisba Optik. Publiclyavailable computer software can be used to analyze the data anddetermine peak-to-valley distance for lens surfaces. The peak-to-valleydistance or value represents the distance between a high point and anadjacent low point of a contact lens. The value is indicative of themagnitude of the surface defect where a value closer to 0 representslittle or no defect and the magnitude of the defect or surface textureincreases as the value increases. The distance can be measured as theperpendicular distance from the peak to the adjacent valley. Morespecifically, the system can utilize wave-front analysis to fit thepropagated waveform reflected from a surface using a set of orthogonalZemike terms, as understood by persons of ordinary skill in the art. Aspecific set or defined set of Zernike terms can be fit to thewave-front of the surface, and the symmetric or regular features of thesurface can be filtered out using the Zernike terms. The residualresulting from the fitting will include the other irregular features ofthe surface.

The irregular features of the lenses with surface wave textures ororange peel textures cannot be adequately fitted with the Zernike terms.Thus, the residual wave-front fit can be used to quantify the waves andmottling of the surface, and characterize them by peak-to-valleydistance, for example. For example, a wave-front surface can be fit withZernike terms up to 10 orders. The magnitude of the waves or mottling isdetermined by removing all of the symmetric or regular terms of thesurface deviations and examining the resulting peak-to-valley value.

Using an interferometer, as described herein, peak-to-valley distancesof contact lenses with wavy or mottled surfaces were observed as smallas 0.18 micrometers. For example, in a batch of contact lenses,undesirable surface wave texture had a peak-to-valley distance from 0.18micrometers to 1.07 micrometers, where the 0.18 micrometers was thevalue for a lens surface with a relatively small amount of waving, andthe 1.07 micrometer value was the value for a lens surface with arelatively large amount of waving. In another batch of lenses, thepeak-to-valley distance for a lens with a mottled lens surface was from0.18 micrometers to 0.35 micrometers.

FIG. 2, as described herein, provides images of a batch of contactlenses obtained from contact lens molds injection molded using apolypropylene resin having a melt flow rate of 1.9 g/10 min. Theselenses are characterized by mottled or wavy lens surfaces, or both.

FIGS. 3 and 4, as described herein, provide images of batches of contactlenses obtained from contact lens molds injection molded using apolypropylene resin having a melt flow rate from about 10 g/10 min toabout 40 g/10 min. These lenses are characterized as having enhancedsurface qualities, that is being free of surface waves or mottlinghaving a peak-to-valley value of at least 0.18 micrometers, such asdetermined using μPhase® FST 10 interferometer, or similar device.

FIG. 5A is a line illustration of an example of a contact lens, similarto a contact lens shown in FIG. 3 or FIG. 4, that has an enhancedsurface quality, that is, a surface that is free of surface waves ormottling having a peak-to-valley value of at least 0.18 micrometers. Inother words, if the lens has some surface waving or mottling and thepeak-to-valley value is less than 0.18 micrometers, it is not visuallyapparent at 28× magnification using a knife edge optical system, asdetermined using an interferometer and wavefront analysis, then the lensis deemed to have enhanced surface quality as a result of beingmanufactured by the lens mold provided in accordance with aspects of thepresent invention. Different zones of the contact lens can be visuallyidentified, such as the central optical zone, an immediately adjacentperipheral zone circumscribing the central optical zone, and animmediately adjacent edge zone circumscribing the peripheral zone.

FIG. 5B is a line illustration of an example of a contact lens, similarto a contact lens shown in FIG. 2 In this example, the contact lens hasa wavy surface, represented by the curved arcs which are reflections orshadows observed with the knife edge optical system. The peak-to-valleyvalue for the wavy lens surface is at least 0.18 micrometers. The waves,represented by the reflections or shadows, are undesirably present inthe central optical zone.

FIG. 6A is a line illustration of a cross-section of an example of acontact lens obtained from the present contact lens mold assemblies. Asillustrated, the contact lens has relatively smooth surfaces that can bedescribed mathematically. As an example, the surfaces do not havevisibly identifiable waves or peaks and valleys, and if they do have anypeaks and valleys, the peak-to-valley distance is less than 0.18micrometers. It will be understood that this cross-section of a contactlens is a simplified illustration of a contact lens, and that actualcross-section images may show different thickness configurations and mayshow visible junctions between different zones of the contact lens.

FIG. 6B is a line illustration of a cross-section of an example of acontact lens obtained from a contact lens mold assembly comprising twomold members formed from an injection molded polypropylene resin havinga melt flow rate of 1.9 g/10 min. The anterior surface is illustrated ashaving an irregular surface characterized by peaks and valleys. Thepeaks and valley distances of such a lens surface is at least 0.18micrometers.

FIG. 7A is an example of a thickness profile for a contact lens obtainedfrom the present contact lens mold assemblies. The thickness increasesfrom one lens edge toward a radial inward point, which can be near theouter border of the optic zone, and then decreases slightly in the opticzone, and increase and decrease again as the thickness is measured tothe diametrically opposed lens edge. Again, this graph is provided forillustrative purposes only and other graphs or thickness profiles mayappear different due to actual lens designs, the meridians along whichthe cross-section is obtained and the like.

FIG. 7B is an example of a thickness profile for a contact lens obtainedfrom a contact lens mold assembly comprising two mold members formedfrom an injection molded polypropylene resin having a melt flow rate of1.9 g/10 min. Since one or both of the lens surfaces are characterizedby visually identifiable peaks and valleys having a peak-to-valleydistance of at least 0.18 micrometers, the thickness profile isirregular across the diameter of the lens section.

The present molds and methods can result in polymerized contact lensproducts, such as pre-extracted or pre-hydrated contact lens productsthat have enhanced commercial acceptability rates compared topolymerized contact lens products obtained from molds and methods usinga thermoplastic polyolefin resin having a melt flow rate of less than 10g/10 min, such as 1.9 g/10 min.

The present molds may be provided so that the first and second moldmembers are structured to be snap-fitted together or press fittedtogether or other forms of interference fitting together using one ormore structural features on the first and/or second mold members toprovide the interference fit. When certain silicone hydrogel contactlens formulations are placed in the present polypropylene molds, and areused to produce silicone hydrogel contact lenses, it is possible toobtain polypropylene molded silicone hydrogel contact lenses thatcomprise anterior and posterior surfaces with ophthalmically acceptablesurface wettabilities, and which are free of surface treatments orpolymeric wetting agent interpenetrating polymer networks that providewettability to lens surfaces of silicone hydrogel contact lenses.

In view of the present disclosure, it can be appreciated that a specificembodiment of the present invention relates to a contact lens moldassembly comprising, consisting essentially of, or consisting entirelyof, first and second polypropylene mold members having one or more ofthe following features: a melt flow rate greater than 10 g/10 min andless than about 40 g/10 min, as determined using the ASTM D1238 testmethod; a density of about 0.900 g/cm³, as determined using the ASTMD1505 test method; a linear flow mold shrink from about 0.010 to about0.020 in/in, as determined using the ASTM D955 test method; a tensilestrength of about 5600 psi, as determined using the ASTM D638 testmethod; a tensile elongation at yield of about 8.0%, as determined usingthe ASTM D638 test method; a flexural modulus from about 200,000 psi toabout 290,000 psi, as determined using the ASTM D790 test method; and aRockwell hardness of about 110, as determined using the ASTM D785 testmethod. In certain embodiments, the present mold members comprise eachof the foregoing features.

Another specific embodiment of the present invention relates to acontact lens mold assembly comprising first and second polypropylenemold members that comprise, consist essentially of, or consist entirelyof a polypropylene resin currently available from Huntsman Corporation(Longview, Tex.) as product identification numbers P4C6N-041NT orP4C5N-046NT. These polypropylene resins have the features described inthe preceding paragraph. These contact lens mold members can be made bypurchasing or obtaining these polypropylene resins from HuntsmanCorporation and injection molding the obtained polypropylene resin intocontact lens mold members using conventional injection moldingtechniques. For example, these polypropylene resins can be injectionmolded into the present contact lens mold members using a melttemperature from 210° C. to 240° C.; a cooling water temperature from20° C. to 50° C.; an injection time in the filling phase from 0.2seconds to 1.5 seconds; a back pressure from 20 bars to 200 bars; aholding and packing pressure from 50% to 150% of the peak injectionpressure. First and second mold members can be placed together, such aspress-fit together, to form the present contact lens mold assemblies.

Accordingly, aspects of the present invention include contact lenses andmethods of using and making contact lenses that have enhanced surfacequality relative to identically produced lenses and methods involving athermoplastic polyolefin resin having a materially significant melt flowrate, which may be referred to as a comparative class of lenses. Inspecific aspects of the present invention, the enhanced surface qualitycharacteristics include a decrease in lens defects, which can bemeasured by quantifying a decrease in depth and/or length values ofsurface imperfections or textures of the produced lenses compared to thecomparative class of lenses. In a preferred embodiment, the enhancedsurface quality comprises a decrease of the depth of the surface defectscompared to the comparative class of lenses. For example, the presentcontact lenses have surfaces with textures having a peak-to-valleydistance from about 0 micrometers to less than 0.18 micrometers.

The foregoing contact lens mold assembly can comprise a polymerizablelens precursor composition or a polymerized lens product located betweenthe first and second mold members, such as in a lens shaped cavityformed by the first and second mold members. The polymerizable lensprecursor composition can comprise a silicone containing material, aHEMA containing material, and combinations thereof.

The following non-limiting examples illustrate certain aspects of thepresent invention.

EXAMPLE 1 (Comparative)

A commercial quantity (10,000) of soft hydrogel contact lenses, similarin composition to the Biomedics™ 55 contact lenses sold by CooperVisionInc. (ocufilcon D), are produced using conventional cast moldingprocessing. The molds are made of a polypropylene resin sold by Finaunder the tradename Fina PPH 3066. This resin does not include anucleating agent. The melt flow rate of this polypropylene resin is 1.9g/10 min.

The lenses produced are associated with an undesirable number of surfacedefects or imperfections, such as waves, and orange peeling texture,also known as mottling, as well as other surface defects orimperfections. These imperfections are visibly identifiable usingconventional methods and devices, including magnifying instruments orlens inspection equipment. FIG. 2 includes a series of picturesillustrating a number of the surface imperfections of contact lenses,which occur using this polypropylene resin as the mold material. As canbe seen in FIG. 2, many of these surface imperfections are quite severe.It should be noted that the defects shown in FIG. 2 are other thanholes, chips and tears in the lenses.

All of the lenses shown in FIG. 2 result in inferior optical quality andinferior vision. Since there can be a relatively large number of lenseswith such surface defects (e.g., about 30% of the lenses are categorizedas having wavy surface texture or orange peel surface texture), thedefective lenses lower customer satisfaction and adversely affectproduct competitiveness. The defects are identified visually using aknife edge optical system, as understood by persons of ordinary skill inthe art, at a magnification of 28×. The sensitivity of the surfacedefect identification is dependent on the resolution of the magnifyingdevice, as understood by persons of ordinary skill in the art.

EXAMPLE 2

Example 1 is repeated except that the molds are made of a nucleatedpolypropylene resin provided by Huntsman under the tradenameP4C6N-041NT. This resin has a melt flow rate of 35 g/10 min, asdetermined using the ASTM D1238 test method.

The lenses produced have a reduced incidence of (fewer) surfaceimperfections than the lenses produced in Example 1. For example, thelenses for Example 2 with imperfections is decreased or reduced by atleast 90% or at least 95% relative to the lenses of Example 1. In otherwords, contact lenses produced using the Huntsman P4C6N-041NTpolypropylene resin can be produced with an acceptability rate of atleast 90% or at least 95%, that is at least 90% or at least 95% of thecontact lenses meet manufacturing inspection criteria and are packagedfor further processing, such as sterilization and distribution. It canalso be understood that the contact lenses obtained from the presentmolds have a correspondingly lower surface defect rate, such as surfacetextures that have the visual appearance of waves or orange peel.

In addition, the severity of the imperfections in the lenses of Example2, when such defects did occur, is reduced relative to the severity ofthe imperfections of the lenses of Example 1. For example, as measuredby the depth and/or the length of a surface imperfection, the severityof the average surface imperfection of the lenses of Example 2 isdecreased or reduced by at least 90% or at least 95% relative to thelenses of Example 1. For example, the average depth of a surfaceimperfection of a batch of lenses of Example 2 that have surfaceimperfections can be about 10% or less, such as 5%, compared to theaverage depth of a surface imperfection of a batch of lenses of Example1 that have surface imperfections. In addition, the average length of asurface imperfection of a batch of lenses of Example 2 that have surfaceimperfections can be about 10% or less, such as 5%, compared to theaverage length of a surface imperfection of a batch of lenses of Example1 that have surface imperfections.

FIG. 3 includes a series of pictures of a representative number oflenses produced in accordance with Example 2. No lenses that areproduced in accordance with Example 2 have surface imperfections morenumerous or more severe than do the lenses shown in FIG. 3.

EXAMPLE 3

Example 1 is repeated except that the molds are made of a nucleatedpolypropylene resin provided by Huntsman under the tradenameP4C5N-046NT. This resin has a melt flow rate of 20 g/10 min, asdetermined using the ASTM D1238 test method.

The lenses produced have a reduced incidence of (fewer) surfaceimperfections than the lenses produced in Example 1. For example, thelenses for Example 3 with imperfections is decreased or reduced by atleast 90%, or at least 95%, relative to the lenses of Example 1. Inother words, contact lenses produced using the Huntsman P4C5N-046NTpolypropylene resin can be produced with an acceptability rate of atleast 90%, or at least 95%, that is at least 90% or at least 95% of thecontact lenses meet manufacturing inspection criteria and are packagedfor further processing, such as sterilization and distribution. It canalso be understood that the contact lenses obtained from the presentmolds have a correspondingly lower surface defect rate, such as surfacetextures that have the visual appearance of waves or orange peel.

In addition, the severity of the imperfections in the lenses of Example3, when such defects did occur, is reduced relative to the severity ofthe imperfections of the lenses of Example 1. For example, as measuredby the depth and/or the length of a surface imperfection, the severityof the average surface imperfection of the lenses of Example 3 isdecreased or reduced by at least 90% or at least 95% relative to thelenses of Example 1. For example, the average depth of a surfaceimperfection of a batch of lenses of Example 3 that have surfaceimperfections can be about 10% or less, such as 5%, compared to theaverage depth of a surface imperfection of a batch of lenses of Example1 that have surface imperfections. In addition, the average length of asurface imperfection of a batch of lenses of Example 3 that have surfaceimperfections can be about 10% or less, such as 5%, compared to theaverage length of a surface imperfection of a batch of lenses of Example1 that have surface imperfections.

FIG. 4 includes a series of pictures of a representative number oflenses produced in accordance with Example 3. No lenses that areproduced in accordance with Example 3 have surface imperfections morenumerous or more severe than do the lenses shown in FIG. 4.

The polypropylene resins used in Examples 2 and 3, in accordance withthe present invention, have better melt flow properties and are easierto process into contact lens molds than is the polypropylene resin usedin Example 1. In addition, the polypropylene resins used in Examples 2and 3 have passed all tests including, without limitation,processability tests, leachability tests, cytotoxicity tests (on thelenses produced) and clinical performance tests (on the lensesproduced). The Example 2 and 3 resins have resulted in better moldsurface quality and better contact lens surface quality relative to theExample 1 resin. In addition, the Example 2 and 3 resins advantageouslyrequire reduced processing temperature and pressure, and may provide forreduced cycle time relative to the Example 1 resin.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the following claims.

1. A method of producing soft cast-molded contact lenses having reducedoptical distortion, the method comprising: providing first and secondmold members structured to be assembled together to form a lens-shapedcavity therebetween, each of the first and second mold members comprisesa nucleated thermoplastic polyolefin resin having a melt flow rate in arange from about 20 g/10 min to about 40 g/10 min as measured using testmethod ASTM D1238 at conditions of 230° C. with a load of 2.06, whereinan amount of nucleating agent is about 0.1% to about 1.5% (wt/wt);providing a contact lens-forming composition in the cavity; forming acast-molded contact lens product from the contact lens-formingcomposition in the cavity; removing the cast-molded contact lens productfrom the first and second mold members; and repeating the providing,placing, forming and removing steps a plurality of times to produce aplurality of soft cast-molded contact lens products having reducedoptical distortion relative to an identically produced plurality of softcast-molded contact lens products made using first and second moldmembers comprising a thermoplastic olefin resin having a melt flow rateof 1.9 g/10 min; wherein the reduced optical distortion of the lensescomprises a reduced number of lenses with optical distortions that arevisually apparent at 28× magnification using a knife edge opticalsystem, as determined using an interferometer and wavefront analysis. 2.The method of claim 1 wherein the placing and subjecting steps arerepeated at least about 100 times.
 3. The method of claim 1 wherein theplurality of soft cast-molded contact lens products are hydrogel contactlens products.
 4. The method of claim 3 wherein the nucleatedthermoplastic polyolefin resin is a nucleated thermoplasticpolypropylene resin.
 5. The method of claim 1 wherein the plurality ofsoft cast-molded contact lens products are silicone hydrogel contactlens products.
 6. The method of claim 5 wherein the nucleatedthermoplastic polyolefin resin is a nucleated thermoplasticpolypropylene resin.
 7. The method of claim 1 wherein the nucleatedthermoplastic polyolefin resin is a nucleated thermoplasticpolypropylene resin.
 8. The method of claim 1 wherein the forming stepcomprises polymerizing the contact lens-forming composition.
 9. Themethod of claim
 1. wherein each of the first and second mold membershave (i) a density of about 0.900 g/cm³; (ii) a linear flow mold shrinkfrom about 0.010 to about 0.020 in/in; (iii) a tensile strength of about5600 psi; (iv) a tensile elongation at yield of about 8.0%; (v) aflexural modulus from about 200,000 psi to about 290,000 psi; or (vi) aRockwell hardness of about 110, or combinations thereof.
 10. The methodof claim 9, wherein the first and second mold members comprise each ofthe features (i) through (vi).
 11. The method of claim 1, wherein theremoved contact lens product has an anterior surface and a posteriorsurface, and both surfaces are free of a surface texture having apeak-to-valley value of at least 0.18 micrometers.
 12. The method ofclaim 1 wherein the optical distortions are surface defects of thecontact lenses.
 13. The method of claim 12 wherein the surface defectsof the contact lenses are directly transferred from at least one of thefirst and second mold members during the forming step of the cast-moldedcontact lens.